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error problems between experimental and numerical study

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Old   June 12, 2010, 11:24
Default error problems between experimental and numerical study
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Hello,

i am a spanish man that are doing an aerodynamic study of a motorsport spoiler. I had done a numerical simulation with star ccm+ and now i am taking some information with this spoilers in a wind tunnel. My project tutor/teacher said me that the cfd can be until 20% of error (more or less) between the cfd mesurements and the mesures of wind tunnel. I don't understand because my mesurements in wind tunnel are ok with Drag component but not with Lift component (Downforce).

For example: with 0 degrees inclination the cfd study shows 38,33 N of Downforce and 8,84 N of Drag and the wind tunnel measures are 22,5 N of Downforce and 7,1 N of Drag. If I applicate the teacher's theorem, the drag are in the 20% of error. 7,1 + (20% of 8,84 = 1,77) = 8,87 N but if I do the same with the Downforce the result is not valid with this theory.

Someone know if is true that's the maximum error between cfd and experimental study are 20% or can be more?? What can I do?

Thanks,

david.
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Old   June 15, 2010, 05:23
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Mesh problem, maybe wrong solver.
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Old   June 18, 2010, 01:39
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Can you post a picture of your mesh. As well as tell us your physic models? Then we can try and help!

Are you positive all the boundaries are set right??
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Old   June 18, 2010, 07:34
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Use fine mesh with quality.
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Old   June 18, 2010, 12:45
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Quote:
Originally Posted by CFD_4 View Post
Use fine mesh with quality.
Very helpful... maybe he can't
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